This invention relates to air cleaners, and particularly to electrostatic air cleaners.
Various electrostatic air cleaner designs have been proposed. One significant advantage of electrostatic designs is the possibility to reduce the pressure drop across the air cleaner, when compared to conventional mechanical filter air cleaners. A high pressure drop gives rise to the need for a powerful fan in order to provide the desired air flow rate, causing noisy operation of the air cleaner.
Conventional electrostatic air cleaners comprise a charging section for charging particles in the air stream through the filter, and a dust precipitation section. The pressure drop across the air cleaner can be arranged to be near zero. The charging section typically comprises a high voltage ioniser and may be arranged as a series of corona discharge electrodes, in the form of fine wires, sandwiched between ground plates. The conditions required for corona discharge will be known to those skilled in the art. Essentially, a sufficient electric field strength is required to ionise air molecules in the vicinity of the corona discharge electrodes. The corona electrodes rapidly discharge ions of one polarity while ions of the opposite polarity drift along the electric field lines towards the ground plates. Particles entrained in the air stream become charged through collisions with these drifting ions.
An electrostatic air cleaner employing a corona discharge charging section of this type is described in U.S. Pat. No. 5,330,559.
A problem with electrostatic air cleaners of this kind is the cost and complexity of the components, including the voltage source, as a very high voltage can be required to sustain the corona discharge, for example 6 kV to 20 kV, as described in U.S. Pat. No. 5,330,559.